COFFIN. — THE SELF-INDUCTANCE OF COILS. 803 



functions as above given. It was found that the variable part of the 

 expression for self-inductance agreed identically with that derived for a 

 circular current sheet. This shows that the bending of straight wires 

 into circles, and forming a coil of a single layer therewith, does not affect 

 the way in which the self-inductance varies. 



We believe, then, that Plot I gives very approximately the law 

 according to which the self-inductance falls off for straight ring-shaped 

 conductors, and probably for any simply shaped square or polygonal 

 hollow straight conductors, as well as for circular coils of a single layer, 

 wound with wires of circular, square, or polygonal cross-sections. 



Dept. Physics, 

 Clark University. 



